COVID-19 Vaccine Uptake in Immigrant, Refugee, and Nonimmigrant Children and Adolescents in Ontario, Canada

Key Points Question What are the COVID-19 vaccination rates in immigrant and refugee children (5-11 years) and adolescents (12-17 years) in Ontario, Canada? Findings In this cohort study of 2.2 million minors, vaccine coverage was 53.1% for children (≥1 dose) and 79.2% for adolescents (≥2 doses), and uptake was higher in immigrants and lower in refugees compared with nonimmigrants. There was significant heterogeneity by region of origin in first- and second-generation immigrants and refugees, even after adjusting for immigration category and other sociodemographic factors. Meaning These findings suggest that precision public health approaches are warranted to increase vaccination in some immigrant, and particularly refugee, subgroups.

for asylum through the in-country immigration pathway) (eTable 3 in Supplement 1), time since immigration, region of origin, and generation. First-generation immigrants and refugees were identified by the immigration database. Linked maternal-or birthing parent-infant hospital delivery records were used to assign the immigration characteristics of mothers and birthing parents to their second-generation children (eTable 1 and eTable 2 in Supplement 1). All others were categorized as nonimmigrant minors.

Covariates
Baseline characteristics were recorded on January 1, 2021 (eTable 1 in Supplement 1). Individual-level covariates hypothesized to be associated with vaccination included age, sex, having a pediatric chronic condition, influenza vaccination in 2019 or 2020, primary care model (family practice, pediatrician, community health center, or no regular primary care practitioner), and history of SARS-CoV-2 infection. Socioeconomic characteristics have been reported to be associated with vaccination and are potential mediators between immigrant or refugee status and vaccination. 42 We used the material deprivation construct from the census-based Ontario Marginalization Index, 43 which includes income and education information on a neighborhood level to capture socioeconomic disparities, and previously derived deciles of neighborhood COVID-19 risk 44 based on COVID-19 cases from the beginning of the pandemic until March 23, 2021 (eTable 2 in Supplement 1). 25

Statistical Analysis
We compared baseline characteristics of both generations of immigrants and refugees with nonimmigrants using standardized differences (>0.1 signified important differences). 45 Given the size of the cohort, we did not test differences in crude rates but commented on clinically important differences.
Using logistic regression, we first modeled the association of immigrant category (with nonimmigrants as the reference group) with vaccination in the full study population and included all covariates. To understand the associations among immigration characteristics, we did a subgroup analysis of first-and second-generation immigrants and refugees, stratified by generation, as we hypothesized different associations by generation. We included key mediators, like socioeconomic characteristics (material deprivation quintile) but did not include influenza vaccination and previous SARS-CoV-2 infection, as these models were intended to test which intersecting sociodemographic and immigration characteristics were most strongly associated with vaccination. We compared differences within each generation using 95% CIs of adjusted odds ratios (aORs). To explore if associations between the exposures and vaccine hesitancy were different than those for vaccine uptake, we performed a secondary analysis using time-to-event models to calculate hazard ratios (HRs) associated with first doses. Individuals with missing or suppressed data were merged to the most appropriate category or excluded from the final models (eTable 2 in Supplement 1). Statistical analyses were conducted using SAS statistical software, Enterprise Guide version 7.1 (SAS Institute).
Data were analyzed from May 9 to August 2, 2022.
[21.4%]). Second-generation minors most frequently had mothers or birthing parents originating from South Asia (Table 1). Immigrants, and particularly refugees, were more likely than nonimmigrants to live in neighborhoods with highest material deprivation (first-generation immigrants: 18

Vaccination in Immigrants and Refugees and by Generation
Compared with nonimmigrants, immigrants had higher odds of being vaccinated, an association that persisted after adjustment (children: aOR, 1.30; 95% CI, 1.27-1.33; adolescents: aOR, 1.10; 95% CI, 1.08-1.12) (Figure 1) (Figure 2; eTable 6 and eTable 7 in Supplement 1). For almost all regions of origin with low vaccination rates, the adjusted odds were similarly low in the second generation. Socioeconomic inequities were present in the immigrant-and refugee-only model but less pronounced than in the model including all Ontario minors (eTables 5-7 in Supplement 1).

Time to First Vaccination
The time-to-event analyses showed similar patterns to the logistic regression models ( Table 3).
There was earlier uptake of the first COVID-19 vaccine dose in immigrants compared with nonimmigrants (adjusted HR, 1.05; 95% CI, 1.04-1.06). In the immigrant-and refugee-only model,

Discussion
In this population-based cohort study, COVID-19 vaccination coverage was 53.1% in children and 79.2% in adolescents in Ontario, Canada. Vaccination rates were higher for immigrants and lower for refugees, compared with nonimmigrants. There was significant variation within subgroups of immigrants and refugees by region of origin, with relative differences frequently persisting across generations. Odds of vaccination increased with age, higher socioeconomic status, and lower neighborhood COVID-19 risk. Similar associations were found when analyzing time to first vaccination.     Children were considered vaccinated if they had received at least 1 vaccine dose; adolescents, at least 2 vaccine doses. NA indicates not applicable. a First-generation immigrants are the reference group for other first-generation individuals; second-generation immigrants, other second-generation individuals. b The full cohort of first-generation immigrants and refugees are the reference group for first-generation immigrants and refugees by region of origin; the full cohort of second-generation immigrants and refugees, second-generation immigrants and refugees by region of origin. migrants, a systematic review on routine and COVID-19 vaccination named language, vaccine literacy, and vaccination benefits as additional factors. 49 All of these factors likely contributed to our results.

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Our findings of higher vaccine coverage in immigrants is consistent with a study of adolescents and adults from Alberta, Canada, which found higher vaccine coverage (78% vs 76%) in immigrants compared with nonimmigrants. However, it did not distinguish immigrants and refugees, assess generations, or include children. 50 In our study, refugees, and particularly refugee children, were more likely to be undervaccinated, which is consistent with data on routine and COVID-19 immunizations in European refugees. 10 While potential explanations include different countries of origin or socioeconomic status in refugees compared with other immigrants, we adjusted for both, suggesting an independent association between refugee status and undervaccination. Educational attainment is higher in protected persons than in resettled refugees 51 and may explain differences within refugee groups in our study. Although evidence on parental education and vaccination acceptance is not universal, 52-54 studies from North America, New Zealand, and Europe have reported a positive association. [55][56][57][58][59] Other explanations may be limited language ability or health literacy and lower confidence in vaccine information from the media. 59 We found a high degree of variation by region of origin (the range of differences in rates was 29.5 percentage points for second generation immigrant and refugee adolescents and 53.6 percentage points for immigrant and refugee children). Associations between regions of origin and vaccination were not attenuated after adjustment for socioeconomic and demographic factors. Low rates in immigrants and refugees from Eastern Europe and Central Africa were consistent with other literature, 16 and low uptake has also been documented for citizens in the corresponding home countries. 60 While cross-national frameworks for research on immigrant health are complex and causes for health behaviors highly context-specific, 60  Force on Vaccine Equity were associated with successfully decreasing vaccine hesitancy. 28 Our finding of high vaccine coverage in immigrants and refugees from Southeast Asia correspond with current evidence 60 describing high confidence in vaccinations and health experts in these regions. 69 Contrary to our hypotheses, associations by region of origin, especially in regions with low vaccination, were remarkably stable across generations, suggesting that cultural background influences vaccination decisions over longer periods of time than expected. While there is little comparable literature, this is consistent with a 2019 US study, 70 in which self-reported influenza vaccine coverage was similar across first-and second-generation Arab immigrants.
We found lower material deprivation was associated with higher vaccination coverage. This is consistent with a systematic review by Wang et al 71  Other findings of our study correlate with survey data. Vaccination was higher with each incremental age increase, which was anticipated by parental surveys from Asia, the Middle East, North America, and Europe. [74][75][76][77][78][79] Lower perceived risk of developing severe COVID-19, combined with less confidence in the relatively new COVID-19 vaccine for younger children, were the main reasons reported for vaccine hesitancy. [74][75][76][77][78][79] Lower effectiveness of COVID-19 vaccinations in younger age groups may also contribute to reduced vaccine confidence. 79,80 Limitations This study has some limitations. The use of administrative data and the retrospective design limited our ability to measure potentially important variables, including individual household income, parent or guardian education, language preference and proficiency, routine vaccine uptake, sources of information about COVID-19, peer group influence, and trust in the health system. As testing criteria for SARS-CoV-2 infections changed over time, this variable was limited to infections prior to vaccine eligibility. We had no data on immigrants or refugees who intended to arrive in another province, were undocumented migrants, or were asylum seekers awaiting their hearings, limiting generalizability of our findings to these groups. Additionally, the research took place in a context where publicly funded, equity-focused COVID-19 vaccination campaigns existed, where pediatric vaccination was recommended and promoted, and with distinct immigration policies. While resettled refugees in Canada may be similar to those in other countries, protected persons and immigrants may have different attributes than in other jurisdictions.

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COVID-19 Vaccine Uptake in Immigrant, Refugee, and Nonimmigrant Children and Adolescents

Conclusions
In this Canadian population-based cohort study, nonrefugee immigrant minors had higher vaccine coverage than nonimmigrants. The substantial heterogeneity by region of origin and lower vaccination coverage in refugees persisted across generations. Precision public health approaches should target specific barriers in the identified, undervaccinated subgroups in ongoing vaccine campaigns.